Infrared thermography, whereby infrared cameras are employed to capture infrared images at any one of several infrared wavelength ranges, is known to be a useful tool in a wide variety of applications. An observed anomaly or problem is known as a thermographic "event" to be reported and possibly diagnosed. The invention is disclosed herein in the context of industrial plant maintenance, also known as preventative maintenance or predictive maintenance. Infrared thermography is also useful in a variety of applications other than plant maintenance, such as EPA studies, agriculture, medical technology, law enforcement, veterinary medicine and military uses.
As one example of a plant maintenance application, an infrared image of the interior of a three-phase electric motor switch box may reveal that one fuse out of three, or the fuse connectors, is hotter than the other two, indicating a potential problem to be corrected before an actual failure occurs.
As another example, within a three-phase electrical control box, a conductor associated with one of the phases may be colder than corresponding conductors associated with the other two phases, indicating that less current is being carried, and pointing to a potential problem to be investigated.
As other examples, within the exemplary context of industrial plant maintenance, the following components may advantageously be inspected employing infrared thermography: transformers, transformer control cubicles, motor control centers, transmission lines, electric motors, steam traps, pipes, valves, belts, components subject to vacuum leaks, insulation in general, roofs and roof insulation, dry type transformers, rotary kilns, auxiliary transformers, start up transformers, distribution panel circuit breakers, relays and ground straps.
A large, heavy, bulky thermographic unit can be difficult, if not impossible, to use in many industrial settings. Plant designs are simply inhospitable to the thermographer who is trying to transport his equipment from one measuring location to another. Therefore, portability is a desirable quality in many infrared thermography applications. Another desirable quality is user friendliness and simplicity.
One method of attempting to achieve portability in prior art systems utilizes a hand truck, or dolly, onto which the thermography equipment is attached. The hand truck and equipment can then be moved from one location to another with greater ease. However, in many situations these systems are less portable than needed or desired. A hand truck loaded with heavy, sensitive electronics is difficult to transport up and down stairs, through tight areas, around large equipment, etc.
Another attempted solution to portability known in the prior art utilizes a hand-held unit that is transported without the aid of a hand truck. Unfortunately, these systems achieve portability at the cost of capability. By reducing the size and weight normally associated with other prior art thermography systems, the hand-held systems exclude many desirable functional features.
Video display speed, data processing power, and internal databus speed have been major design obstacles for which the prior art has not satisfactorily overcome. Internal databus transfer rates are simply too slow to eliminate video display flicker. To avoid the problem, a few systems have elected not to digitize the video signal generated by the camera and to simply route the video signal to the display in analog format. While this approach generally works well to eliminate flicker, the analog format reduces the data processing capabilities and overall versatility of the system.
Prior art infrared thermography systems have also been labor intensive, physically cumbersome, and relatively inefficient from the viewpoint of enabling a thermographer to rapidly and efficiently generate reports. For example, if a thermographer desired to annotate the video image by adding text or perhaps an arrow to indicate an area of interest, this would have to be done with the assistance of a base station computer, or perhaps by manually annotating a hard copy of an image. It could not be accomplished in the field.
There are known prior art thermography systems which employ infrared cameras connected to a videotape recorder whereby a thermographer can record infrared images of various pieces of equipment and other objects. Later, when the thermographer is preparing a report, the videotape is played until desired images are found, which are displayed on a screen, and then captured for a permanent record, either photographically off of the video screen, or digitally.
Another prior art approach to thermography employs an infrared camera having what is in effect "snapshot" capability whereby a limited number of thermographic images, for example thirty-three images, may be digitally captured to a floppy disk included within the infrared camera, for later review.
Systems presently exist that combine the use of an infrared camera with a visible image camera. An image from either camera may be recorded onto a videotape. As an alternative to the visible image video camera, a conventional photographic snapshot camera may be used. These systems do not permit the thermographer to analyze images and generate reports in the field, but instead, the thermographer must later correlate the stored images for analysis and report generation back at the lab. Although computers have been utilized as an excellent tool for manipulating the images and performing analyses on the data, the process remains generally slow and cumbersome. Usually, the thermographer must spend many hours searching the numerous videotape images, looking for particular thermographic events to analyze and document, correlating images of interest to perhaps a visible image that was taken, and then generating the report.